Apparatus and method for editing isochronous information transmitted among various devices

ABSTRACT

An apparatus and method for editing isochronous communication data used for communication between various electronic devices. An editing procedure with high accuracy can be conducted without reading the system data of isochronous communication in a system having co-existing isochronous and asynchronous modes of communication for data transmission between the electronic devices. The editing procedure can also be conducted with high accuracy in a system in which an edit controlling device cannot recognize the frame boundary in the information signals. Furthermore, even if there are various time delays associated with the instruction reception and the instruction execution by an electronic device, the editing procedure can be conducted with high accuracy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 08/519,941, filedon Aug. 28, 1995 U.S. Pat. No. 5,790,743.

This application is related to the following co-pending U.S. patentapplications: Ser. No. 08/183,396; Ser. No. 08/373,279; Ser. No.08/403,708; Ser. No. 08/391,019; Ser. No. 08/449,784; Ser. No.08/502,772; and Ser. No. 08/506,477.

BACKGROUND OF THE INVENTION

The present invention relates to a method of editing isochronouscommunication data and an edit controlling device used therefor in asystem of a plurality of electronic devices connected by a communicationcontrol bus in which isochronous and asynchronous modes of communicationcan co-exist for data transmission between the electronic devices.

A system has been considered for connecting a plurality of devices via acommunication control bus in which isochronous communication andasynchronous communication can be present together, such as a serial busaccording to the IEEE-P1394 standard (hereinafter simply referred to as"P1394 serial bus") for communication between the devices. Details ofthe P1394 serial bus are disclosed in "IEEE P1394 Serial BusSpecification" (published on Oct. 14, 1993).

FIG. 10 shows an example of such a system. The system comprises fourdigital video cassette recorders (hereinafter referred to as "D-CAM"),an editing machine (hereinafter referred to as edit controller) and adigital television receiver (hereinafter referred to as "D-TV"). Thedevices are connected to each other by a cable using the P1394 serialbus transmission. Since each of the devices has a function of relayingsignals transmitted via the cable of the P1394 serial bus, thecommunication system is equivalent to a communication system in whicheach of the devices is connected to a common P1394 serial bus.

Signal transmission in the devices having a common bus is conducted bythe time division multiplexing on every predetermined communicationcycle as shown in FIG. 11 (for example, every 125 μs). For the busmanagement of the communication cycle, a device referred to as a cyclemaster transmits a synchronization packet indicating the starting pointof the communication cycle (cycle start packet: hereinafter referred toas the "CSP") to other devices on the bus. The CSP designates the startof data transmission in the communication cycle. The cycle master isautomatically determined by a method specified according to theIEEE-P1394 standard.

Transmission of signals during one communication cycle includes twomodes: isochronous communication for periodically transmitting, forexample, video data or audio data and asynchronous communication fortransmitting, for example, a connection control command, notperiodically but as necessary. The isochronous communication data istransmitted prior to the asynchronous communication data. Channelidentification 1, 2, 3, . . . , N is provided with each of isochronouscommunication packets to distinguish among a plurality of isochronouscommunication packets. After completing the transfer of the isochronouscommunication packets of all channels, a period of time until the nextCSP is used for the transmission of an asynchronous communicationpacket.

FIG. 12 shows a schematic block diagram for each of the devices of FIG.10. Each device comprises an operation section 1, a display section 2, amicrocontroller 3, an isochronous communication data processing block 4and a communication layer processing block 5. However, the editingmachine has no isochronous communication data processing block 4.

The operation section 1 has keys or the like to enable the user tooperate the device. The display section 2 displays, for example, theoperational state of the device. The microcontroller 3 reads the stateof the operation section 1 and prepares various commands fortransmitting the desired instructions to other devices. Further, when itreceives various types of commands from other devices, themicrocontroller 3 controls the isochronous communication data processingblock 4 or the communication layer processing block 5 for executing theprocessing corresponding to the received command. Further, themicrocontroller 3 controls the display in the display section 2 inaccordance with the operational state of the device.

The isochronous communication data processing block 4 is arecording/regeneration processing section or a tuner section for digitalaudio/video signals if the device is D-VTR, a monitor section or a tunersection if the device is D-TV, or a recording/regeneration processingsection or a camera section for digital audio/video signals if thedevice is D-CAM.

The communication layer processing block 5 conducts processingoperations for converting an isochronous or asynchronous communicationpacket between the P1394 serial bus format and the format used by theisochronous communication data processing block 4 or the microcontroller3. The communication layer processing block 5 may also performarbitration processing for a physical layer and a link layer, such asobtaining or aborting the right to use the P1394 serial bus.

In the communication system of FIG. 10, the editing procedure isconducted, for example, by using D-VCR 1 as a playback machine, andD-VCR 2 as a recording machine via the control of the editing machine.The editing in this case is an assemble mode editing by a so-called 1:1edit system of dubbing signals regenerated from a video tape (originaltape) of a playback machine by superimposing the signals on a portion ofan already recorded area on the video tape (master tape) of therecording machine.

In this case, as shown in FIGS. 13C and 13D, the editing machine atfirst controls the playback machine and the recording machine such thatthe original tape and master tape are prerolled from their respectiveregeneration/recording IN points. Then, the editing machine sets theplayback machine and the recording machine to the regenerating mode and,subsequently, sets the recording machine to a recording modesimultaneously with the arrival of the IN point. Then, when the requiredportion is recorded on the master tape, the recording operation isstopped. In this case, external synchronization is applied to therecording machine via a frame sync signal in the regenerated videosignals of the playback machine. The operation of the playback machineand the recording machine is controlled such that the instances at whichrespective tape positions reach the respective IN points coincide witheach other.

For conducting such editing with high accuracy, it is necessary for theediting machine to accurately determine tape position information on theplayback machine and on the recording machine. It is also necessary forthe playback machine and the recording machine to execute an editingcontrol command at the instance designated by the editing machine. Thus,for the editing machine to obtain accurate tape position information onthe playback machine and on the recording machine in the system of FIG.10, it may be necessary to analyze system data added to audio/video datasent by the isochronous communication packet, and to read either anabsolute track number (track number appended sequentially from thebeginning to the end of the tape to each of the tracks) or a time code.However, for the editing machine to analyze the system data, a hardwareequipment is required for separating the system data from theaudio/video data and for analyzing the data.

It may also be necessary to request a time code using an inquiry commandpacket of the asynchronous communication and receive an answer from thecorresponding device. However, the time code transmitted by theasynchronous communication packet may sometimes have a delay in relationto the time code in the system data added to the audio/video datatransmitted by the isochronous communication packet.

Further, since the command sent from the editing machine to the playbackmachine and to the recording machine is transmitted by the asynchronouscommunication packet, there is no time reference for audio/video data.Further, the time at which the editing machine sends a command isdifferent than the time at which the command is actually executed by theplayback machine or the recording machine depending on the variousconditions such as the type of the command.

Although problems have been described in the case of conducting theediting procedure by the communication system of FIG. 10, similarproblems also occur in an editing system in which the editing machinecannot recognize the frame boundary in the video signals in an editingsystem, for example, as shown in FIG. 14, which comprises a plurality ofanalog or digital VCRs connected by analog or digital audio/video signallines and an editing machine, connected to them by control signal lines,for sending and receiving the corresponding command/answer.

SUMMARY OF THE INVENTION

The present invention has been accomplished in view of the foregoingproblems and it is an object thereof to provide an editing method and anedit controlling device capable of executing the editing procedure withhigh accuracy without reading system data transmitted via isochronouscommunication mode.

It is another object of the present invention to provide an editingmethod and an edit controlling device capable of executing the editingprocedure with high accuracy in a system in which an editing machinecannot recognize a frame boundary in video signals.

A further object of the present invention is to provide an editingmethod and an edit controlling device capable of executing the editingprocedure with high accuracy even if there are various time delays fromreception of a command to execution thereof in a playback machine and ina recording machine used as the controlled devices.

According to the present invention, an edit controlling device transmitsa predetermined instruction at a predetermined timing by asynchronouscommunication based on first and second delay times (td), (to) and aboundary position information or a third time information (tf).Accordingly, an editing procedure can be conducted with high accuracywithout reading the system data of isochronous communication. Inaddition, the editing procedure can be conducted with high accuracy evenif there is a time delay from reception till execution of theinstruction in the controlled devices.

Further, according to the present invention, the edit controlling devicetransmits a predetermined instruction at a predetermined timing viacontrol signal lines based on first and second delay times (td), (to)and boundary position information or third time information (tf).Accordingly, an editing procedure can be executed with high accuracyeven in an edit system in which the edit controlling device cannotrecognize the frame boundary position information in informationsignals. Further, the editing procedure can be conducted with highaccuracy even if there is a time delay from reception till execution ofan instruction in the controlled devices.

As has been described above according to the present invention, theediting procedure with high accuracy can be conducted without readingthe system data of isochronous communication in a system in whichisochronous communication and asynchronous communication can be presenttogether.

Further, the editing procedure can be conducted with high accuracy alsoin a system in which the edit controlling device cannot recognize theframe boundary in the information signals. Further, even if there arevarious time delays from reception till execution of an instruction inthe controlled devices, the editing procedure can be conducted with highaccuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for explaining a command processing time delay;

FIG. 2 is a diagram illustrating a command receiving time for ensuring acommand processing time delay;

FIG. 3 is a diagram for explaining processing for detecting a frameboundary from a time code;

FIG. 4 is a diagram illustrating a delay of a time code obtained byasynchronous communication from the time code in isochronouscommunication data;

FIG. 5 is a diagram illustrating an example of isochronous communicationdata and time code in the PB-Pause state;

FIG. 6 is a diagram explaining the processing of adding time informationfrom the top of the frame to the response of the time code;

FIG. 7 is a diagram illustrating processing for extracting frame syncfrom a header of isochronous communication data;

FIG. 8 is a diagram illustrating an example of an editing method towhich the present invention is applied;

FIG. 9 shows a diagram of transmission time for various commands nearvideo recording IN points of FIG. 8;

FIG. 10 is a diagram illustrating an example of a communication systemin which a plurality of devices are connected by a P1394 serial bus;

FIG. 11 is a diagram illustrating an example of a communication cycle inthe P1394 serial bus;

FIG. 12 is a schematic block diagram of a device connected to the P1394serial bus;

FIGS. 13A-13D are diagrams illustrating a relevant editing method;

FIG. 14 is a diagram illustrating an example of a relevant editingsystem.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be explained specifically by way of preferredembodiments with reference to the drawings, by describing: (A) timedelay from reception till execution of a command, (B) a time from thetop of a frame for ensuring the time delay, (C) detection of the top ofthe frame and (D) an example of an editing method to which the presentinvention is applied, in this order.

(A) Time delay from reception till execution of a command. As describedabove, the time at which a control command sent by asynchronouscommunication is received is different than the time at which thecommand is actually executed depending on the kind of the controlcommand, the equipment receiving the control command and the operationalstate of the equipment upon receiving the control command.

Then, the present invention is adapted such that an editing machinerequests each of the devices (D-VCR in this embodiment) the necessarytime for starting a designated operation from the reception of thecontrol command (hereinafter referred to as "command processing timedelay"). The command time delay is defined as td and illustrated in FIG.1.

As shown in FIG. 1, the command processing time delay td is representedon the basis of frame units as time elapsed from the top of the framereceiving the command (an example: td=3 is shown in FIG. 1). An objectfor the inquiry in this embodiment is the following, which is necessaryfor the editing control among various kinds of command processing timedelays:

(1) Command processing time delay requested from the playback machine:

PB-Pause→PB=Delay-P1

PB→PB-Pause=Delay-P2

External sync PB-Pause→external sync PB=Delay-P3

(2) Command processing time delay requested from the recording machine:

REC-Pause→REC=Delay-R1

REC→REC-Pause=Delay-R2

External sync PB-Pause→external sync PB=Delay-R3

External sync PB→REC=Delay-R4

Since the command processing time delay td can take on a different valuewith each transition, the editing machine requests all necessary valuesin accordance with an editing mode from the playback machine and fromthe recording machine using an asynchronous communication packet.

(B) Time from the top of the frame for ensuring a command processingtime delay. The command processing time delay td can thus be obtained.However, since D-VCR is in frame synchronization by reading a header ofisochronous communication data, the timing of starting the execution maysometimes be different depending on the position in the frame (time fromthe top of the frame) of receiving the command. Then, the editingmachine requests a time tc, illustrating the command sending timingelapsed from the top of the frame, to ensure a proper time delay td ineach of the devices. Thus, the command sending timing is determinedbased on tc and td.

The time tc is explained with reference to FIG. 2. When a command isreceived at time "1" elapsed by tc from the top of frame a, the commandexecution is started at time 3 (top of frame d) after the expiration ofthe delay time td. On the other hand, if the command is received at time2 later than the time tc, the command execution is started at time 4 (atthe top of the frame e) later by one frame than the time delay td at theframe c.

If the time from a frame boundary to the command sending timing isalways made constant, the command can be sent without requesting thetime tc.

(C) Detection of the top of a frame. Even if the time tc in the frame isthus recognized, it is further necessary to detect the top of the framefor determining the timing for actually sending the command.

Then, in this embodiment, as shown in FIG. 3, the editing machinerequests a time code continuously during the video data regeneration bythe D-VCR. The editing machine then reconstructs a time code from thechanging point in the time code obtained from a response to the requestfor detection of the frame boundary. In this method, the frame boundaryof video data is aligned only if the time code transmitted by theasynchronous communication has no delay relative to a time code insystem data transmitted by the isochronous communication.

In this respect, in view of the system design of D-VCR, a time codeprovided via the asynchronous communication sometimes makes a delayrelative to a time code in system data transmitted by the isochronouscommunication. Then, as shown in FIG. 4, in this embodiment, a time codecompensated with the time delay is reconstructed to distinguish theboundary of the frame.

The frame boundary can thus be distinguished. However, since anidentical value is always returned for every request about the time codeas shown in FIG. 5 if D-VCR is in a PB (Playback)-Pause state or thelike, the boundary of the frame cannot be detected in this situation.

Then, in this embodiment, two methods are considered for recognizing theframe boundary even if D-VCR is in the PB-Pause state. One of them is toadd time information from the top of the frame as a response to therequest for the time code, as shown in FIG. 6.

The second method is to extract a frame sync from a header of the systemdata in the isochronous communication, as shown in FIG. 7. In this case,the editing machine requires a hardware for extracting the frame syncfrom the header.

(D) Example of an editing method in accordance with the presentinvention. Then, description will be made of conducting the editingprocedure by using the method described above and as shown in FIGS.13A-13D, with reference to FIG. 8.

First, the editing machine requests the time delay to and to from theplayback machine, receives an answer from the playback machine and,successively, requests the time delay to and to from the recordingmachine in the same manner and receives an answer. Further, the editingmachine requests the time delay td from the playback machine andreceives an answer from the playback machine and, successively, requeststhe time delay td from the recording machine and receives an answer. Inthis instance, the playback machine and the recording machine are in thePB-Pause state.

When the delay time is obtained from the playback machine and therecording machine, the tape position in the playback machine isprerolled for a predetermined period of time from the regeneration INpoint (for example, 5 sec.) and, successively, the tape position in therecording machine is prerolled for a predetermined period of time (forexample, for 5 sec) from the recording IN point.

Then, the editing machine sends a play-forward command to the playbackmachine. The playback machine executes the command upon expiration ofthe time delay PB-Pause→PB (Delay-P1) after receiving the command.

Thereafter, the editing machine sets the external synchronizationPB-Pause mode for synchronizing the recording machine using aregenerated video signal of the playback machine.

Further, the editing machine changes the recording machine from theexternal sync PB-Pause to the external sync PB. After receiving thecommand, the recording machine executes it upon expiration of the timedelay (Delay-R3) of the external sync PB-Pause→external sync PB.

When both the playback machine and the recording machine are set in thisway to the regeneration mode, the editing machine requests a time codefrom the playback machine and the video recording machine in order toexamine the tape position in each. Then, the editing machine comparesthe time codes of the playback machine and the video recording machineand controls the running of the tape as required, such that the playbackmachine reaches the regeneration IN point simultaneously with therecording IN point. Then, the editing machine sends a recording command(normal-REC) at an instance earlier than the time delay (D-R4) ofexternal sync PB →REC from the recording IN point, so that the recordingmachine is set accurately to the recording mode at the recording INpoint.

FIG. 9 shows the sending timing for various commands near the recordingIN point of FIG. 8. This is an example for distinguishing the frameboundary based on the frame sync as has been explained previously withreference to FIG. 7. The present invention can also be constituted suchthat a time information tf from the top of the frame is added as theanswer to an inquiry for the time code, as explained previously withreference to FIG. 6.

The foregoing embodiment concerns the 1:1 edit system assemble mode, butthe present invention is applicable also to an A-B roll edit system oran insert mode editing procedure.

Further, the foregoing embodiment relates to the editing procedure in acommunication system in which audio-video devices are connected by theP1394 serial bus. However, the present invention is applicable also toan edit system in which the editing machine cannot recognize the frameboundary in video signals in the edit system of FIG. 14, which comprisesa plurality of analog or digital audio/video signal lines and an editingmachine connected by control signal lines for sending and receivingcommands and answers, respectively. In this embodiment, communicationvia the audio/video signal lines corresponds to the isochronouscommunication in the P1394 serial bus and communication via the controlsignal lines corresponds to the asynchronous communication.

What is claimed is:
 1. A method for editing information signals arrangedin sections in a system having a plurality of devices interconnected viainformation signal lines and information control lines, said devicesincluding an edit control device for controlling, via a plurality ofpredetermined commands transmitted via said information signal lines,editing of said information signals at other devices in said pluralityof devices, said method comprising the steps of:transmitting by saidedit control device a first command of said predetermined commands torequest, via said information control lines, a first time delay from oneof the other devices, said first time delay being an elapsed timebetween receipt and execution of one of said predetermined commands bysaid one of the other devices; transmitting by said edit control devicea second command of said predetermined commands to request from said oneof the other devices, via said information control lines, a time code ofeach section and time position information measured from a beginning ofeach section; determining a second time delay between said time codereceived by said editing device and an actual time code in saidinformation signals; and transmitting by said edit control device athird command of said predetermined commands to perform editing of saidinformation signals based on said first time delay, said second timedelay, said time code and said time position information.
 2. A methodaccording to claim 1, wherein said one of the other devices is a digitalvideo cassette recorder.
 3. A method according to claim 1, wherein saidone of the other devices is a digital editing device.
 4. A system forediting information signals arranged in sections in a configurationhaving a plurality of devices interconnected via information signallines and information control lines, said devices including one devicefor controlling, via a plurality of predetermined commands transmittedvia said information signal lines, editing of said information signalsat other devices in said plurality of devices, said systemcomprising:means for transmitting a first command of said predeterminedcommands to request, via said information control lines, a first timedelay from one of the other devices, said first time delay being anelapsed time between receipt and execution of one of said predeterminedcommands by said one of the other devices; means for transmitting asecond command of said predetermined commands to request from said oneof the other devices, via said information control lines, a time code ofeach section and time position information measured from a beginning ofeach section; means for determining a second time delay between saidtime code received and an actual time code in said information signals;and means for transmitting a third command of said predeterminedcommands to perform editing of said information signals based on saidfirst time delay, said second time delay, said time code and said timeposition information.
 5. A system according to claim 4, wherein said onedevice is an edit control device.
 6. A system according to claim 4,wherein said one of the other devices is a digital video cassetterecorder.
 7. A system according to claim 4, wherein said one of theother devices is a digital editing device.